Normally, the first and second vehicle are at first joined together mechanically via a coupling. By coupling is meant, for example, a fifth wheel, into which a king pin arranged at the trailer side is introduced via a wedgelike tapering entry opening and can be locked together with the fifth wheel. In older vehicles, the fixed supply lines installed on the first vehicle are then connected by the driver by hand to the second vehicle, making use of plug-in couplings. The supply lines include both pressurized air lines and current conducting cables, sometimes also hydraulic lines, and they are provided with energy from an energy supply trunk of the first vehicle. The energy supply trunk for pressurized air includes, for example, a compressor and a pressurized reservoir, and that for the electrical supply includes a generator and a storage battery. Also located on the trailer is an energy distribution trunk for the particular electric, pneumatic or hydraulic energy required.
This includes lines going to the individual consumers and sometimes also an energy storage device, especially when additional systems are hooked up on the trailer, such as refrigeration systems or a mobile fork lift truck. The energy storage device can also be configured as a storage battery or a pressurized reservoir.
To relieve the burden on the driver, there have already been efforts in the past to automate the connecting of the supply lines by means of specially configured plug-in coupling systems. One such plug-in coupling system is disclosed, for example, in DE 101 55 056 A1. Here, a wedgelike support element, in which a plug is arranged, can swivel and engage with the king pin of the trailer. During the coupling process, the wedgelike support element is oriented by the entry opening, which is complementary in form and also wedgelike, and it is secured laterally in the final locked position. In this form-fitting secured position, a movably mounted plug socket is extended from one side of the entry opening and engages with the plug located in the support element.
The invention is addressed to such plug-in coupling systems in which the connection of the plug-in coupling is accomplished without manual intervention of a person, since it is possible for a breakage or a major leak to occur at the plug-in coupling system during the driving on account of wear and tear or a mistake in operating the vehicle. Automated plug-in coupling systems are especially affected by this, due to vibrations and the relative motions which can occur when hooking up and unhooking the trailer, and also during the driving. Therefore, it is not always possible to ensure a reliable contacting and, thus, a trustworthy energy transmission. This may at times result in serious consequences.
For example, leakage of a pressurized air line could result in a sudden loss of pressurized air and the trailer would suddenly and unexpectedly undergo a complete braking.
Another prior art is disclosed by DE 39 07 762 A1 with a brake system for a tractor-trailer rig, wherein the brake system comprises a discharging circuit on the trailer and a charging circuit arranged on one of the two vehicles. The discharging circuit is formed by an energy storage in the form of a battery, a charging and discharging device connected in series with it, a control unit and valve units interacting with the latter, and the corresponding lines. The charging circuit comprises an energy source of the tractor, for example, a generator, the charging and discharging device, and the energy storage. During the braking process, relatively large currents flow through the lines of the discharge circuit, which can be designed relatively short on account of the near physical proximity of the energy storage to the control unit and therefore they produce only a slight voltage drop. The energy put out from the energy storage is made up during the nonbraking time by the electric energy source via the charging circuit. Since the nonbraking time is very much greater than the brake operation time, the energy storage can have its charge replenished with low currents over relatively long lines with little voltage drop.